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[Reference Hurley, Kocun, Revenko, Ohler and Proksch 26] A feasible and facile method to prepare cement paste sample for AFM scanning is to cast pristine cement paste on flat substrate to generate a replication surface, such as the mica-replication method, which results in a surface with z-heights of 4–20 nm. [Reference Yang, Keller and ...
cement, usually used in refractory, building materials, petroleum and electric power industries due to its high temperature resistance performance, high early ... and 45 0C, the NO3-AFm phase is formed, and able to bypass the formation of the metastable phases. Furthermore, the efficiency of the approach is …
Sep 15, 2017· Even using atomic force microscopy (AFM), which is a very high resolution type of scanning probe microscopy (with lateral resolution of ~30 nm, vertical resolution of up to 0.1 nm), if a particular phase is identified for indentation, the results from nanoindentation will reflect the composite properties, as the computational models are in ...
deterioration of concrete due to the compound effect of chloride ions ingress and carbonation following models are needed:(1) a model of cement hydration, i.e. the formation model of AFm phase; (2) a model for describing the fixation of chloride ions in AFm phase, i.e. the formation model of Friedel's salt; (3) models applied to characterize
Oct 30, 2015· Cement could also be blended with limestone, mainly CaCO 3, and atmospheric CO 2 is readily uptaken by wet cements pastes cured in the open. In this way, sulfate and carbonate phases form normally in the hydration process of cement paste. We know that AFm and AFt are common sulfate and carbonate bearing phase product of cement hydration.
AFM – atomic force microscopy C. 3. S – tricalcium silicate Ca - calcium CH – calcium hydroxide COMPASS – Condensed-phase Optimized for Atomic Simulation Studies C-S-H – calcium silicate hydrate E – Young's modulus E. i – Young's modulus of the indenter E. r – reduced modulus ERDC – Engineer Research and Development Center
During the hydration of cement, tricalcium aluminate (C3A) reacts with gypsum and forms ettringite (AFt). Once all gypsum is consumed, ettringite can further react with remaining C3A and form monosulfate (AFm) at 1–2 days. Normally, at early ages, ettringite all transfers to AFm phase. After several months or years, ettringite can form again if a new source of sulfate becomes available in ...
Abstract Ettringite (AFt) and monosulfoaluminate (AFm(MS)) are the two of the main hydration products of tricalcium aluminate. Ettringite formation is favored in the presence of gypsum, and monosulfoaluminate is the usual AFm phase in a system with low calcium carbonate content. In this article, a new empirical force field, AFFF, is proposed to describe the interactions among species in ...
Feb 01, 2007· The AFm phase of Portland cements refers to a family of hydrated calcium aluminates based on the hydrocalumite-like structure of 4CaO·Al 2 O 3 ·13–19 H 2 O. However OH − may be replaced by SO 4 2− and CO 3 2−.Except for limited replacement (50 mol%, maximum) of sulfate by hydroxide, these compositions do not form solid solutions and, from the mineralogical standpoint, …
In the cement system, the presence of ettringite depends on the ratio of calcium sulfate to tri-calcium aluminate (C 3 A); when this ratio is low, ettringite forms during early hydration and then converts to the calcium aluminate monosulfate (AFm phase or (Al 2 O 3-Fe 2 O 3-mono)). When the ratio is intermediate, only a portion of the ...
The AFm phase in Portland cement. Cement and Concrete Research, 2007. Barbara Lothenbach. Fredrik Glasser. Thomas Matschei. Download PDF. Download Full PDF Package. This paper. A short summary of this paper. 37 Full PDFs related to this paper. Read Paper. The AFm phase in Portland cement. Download.
other AFm phase. The stiffening of cement paste will be monitored using both oscillatory shear rheology and modified ASTM C403 penetration resistance test. The validity of penetration resistance test for monitoring stiffening of cement paste has been thoroughly …
MOTIVATION Aluminous Ferrous Mono (AFm - ) phases with a general chemical composition [Ca2(Al,Fe)(OH)6]+[½ Y or X ·nH 2O]-Y = divalent anion, X = monovalent anion, crystallize during the hydration process of cementitious products. Those phases are members of a large family, the so called LDHs (layer double hydroxides), which are of technical and applied interest in industry due to their ...
Influence of graphene oxide as dispersed phase in cement mortar matrix in defining the crystal patterns of cement hydrates and its effect on mechanical, microstructural and crystallization properties S. Sharma and N. C. Kothiyal, RSC Adv., 2015, 5, 52642 DOI: 10.1039/C5RA08078A
The ability of cement phases carrying positively charged surfaces to retard the mobility of (129)I, present as iodide (I(-)) in groundwater, was investigated in the context of safe disposal of radioactive waste. ... chloride-, carbonate- and sulfate-containing AFm phases indicated that calcium-monosulfate (AFm-SO(4)) is the only phase that ...
May 05, 2015· easily substituted for Cl in the Friedel phase forming chromate-AFm. The chemical formula of chromate-AFm was characterised as 3CaO·Al 2 O 3 ·CaCrO 4 ·12H 2 O. Chromate-AFm gave two steps of dehydration, two steps of dehydroxylation and one step of redox reaction of Cr(VI) in the whole heating process from 40 to 1000°C. The Fourier transform infrared spectra showed different OH …
Jul 01, 1999· OSTI.GOV Journal Article: Synthesis and characterization of sulfite-containing AFm phases in the system CaO-Al{sub 2}O{sub 3}-SO{sub 2}-H{sub 2}O
Mar 14, 2016· Cement hydration products. The main products of cement hydration reactions are calcium silicate hydrate (CSH), calcium hydroxide (CH), and the AFt and AFm phases. The AFt and AFm phases found in hydrated cement are compounds of C 3 A, anhydrite and water. The most common AFt phase is ettringite and the most prevalent AFm phase is monosulfate.
Y1 - 2015. N2 - The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states ...
May 21, 2018· This type of stacking defect has been described repeatedly for AFm during SO 4 2− /I − exchange 8, for C-S-H (the main cement phase) 43,56, and more generally for …
2.The most abundant hydrated cementitious phase, and the phase that contributes most to strength and durability is: C-S-H CH AFt AFm C$ Question: 1.Gypsum (calcium sulfate) is added to slow down the reaction of the "speed demon" in in ordinary portland cement. The fastest reacting component in portland cement is the (use cement chemistry ...
In the cement system, the presence of ettringite depends on the ratio of calcium sulfate to tri-calcium aluminate (C3A); when this ratio is low, ettringite forms during early hydration and then converts to the calcium aluminate monosulfate (AFm phase or (Al2O3-Fe2O3-mono)).
AFm phases, called also (Al2O3-Fe2O3-mono), are a common term for the hydration products with general formula [Ca2(Al,Fe)(OH)6∙(X)]∙y H2O, where X means e.g. OH-, SO42-, CO32-. AFm phases are formed when the corresponding phases are present in adequate concentrations in the solution under the room temperature. The incorporation of sulfite anions in the structure of lamellar AFm phase will ...
An AFm phase is an "alumina, ferric oxide, monosulfate" phase, or aluminate ferrite monosulfate, or Al 2 O 3, Fe 2 O 3 mono, in cement chemist notation.AFm phases are important in the hydration of hydraulic cements.. They are crystalline hydrates with general, simplified formula 3CaO·(Al,Fe) 2 O 3 ·CaSO 4 ·nH 2 O. They form inter alia when tricalcium aluminate (C 3 A: 3CaO·Al 2 O 3) reacts ...
Feb 01, 2007· The AFm phase of Portland cements refers to a family of hydrated calcium aluminates based on the hydrocalumite-like structure of 4CaO center dot Al2O3 center dot 13-19 H2O. However OH- may be replaced by SO42- and CO32-. Except for limited replacement (50 mol%, maximum) of sulfate by hydroxide, these compositions do not form solid solutions and ...
Cement and Concrete Research 35 (2005) 1438 – 1446 Electrical conductivity and phase composition of calcium aluminate cement containing air-cooled and water-cooled slag at 20, 40 and 60 8C M. Heikala,*, M.S. Morsyb, M.M. Radwanc a Chemistry Department, Faculty of Science, Zagazig University, Benha Branch, Benha, Egypt b Building Physics Department, Building Research Center, …
Aug 15, 2018· Other AFm phases, such as hemicarboaluminate and monocarboaluminate, are detected (10·75° and 11·5° 2θ) as a result of reaction of the small amount of calcite in the cement (as identified by XRD, Figure 4) during hydration, and potentially some superficial carbonation contamination of …
Feb 14, 2012· The AFM measured uniaxial viscoelastic compliance values are compared to similar values obtained with traditional nanoindentation for the same material. The comparison of these results shows that the calcium silicate hydrate (C-S-H) phase of portland cement has similar but distinct properties on the sub micron scale than on the micron scale.
amounts of sulfate. Cement could also be blended with limestone, mainly CaCO 3, and atmospheric CO 2 is readily uptaken by wet cements pastes cured in the open. In this way, sulfate and carbonate phases form normally in the hydration process of cement paste. We know that AFm and AFt are common sulfate and carbonate bearing phase product of ...
The most common phase in cement clinkers is β-belite. The reaction rate of β-belite is very slow compared with the one of alite. Therefore is it not very important for the early strengthening phase in cement. On the other hand, it is important for the strength of the final hardened cement. 3.5 Aluminate C 3
Feb 15, 2007· However, in cement science, hydrocalumite is an AFm phase (Matschei et al. 2007; Tian and Guo 2014). This compound could be formed as the …
The determination of reliable weathering/dissolution rates for cement phases is of fundamental importance for the modelling of the temporal evolution of both radioactive waste repositories and CO 2 geological storage sites (e.g. waste matrix, plug in boreholes). Here, the dissolution kinetics of AFm-Cl (hydrated calcium aluminates containing interlayer Cl) has been studied using flow-through ...
The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively ...